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In this communication, a dual-band shared aperture antenna is presented. The proposed antenna achieves dual-band operation by housing both a low-frequency patch antenna array and a high-frequency reflectarray in the same aperture area. The two different antenna types are combined into a single antenna product without any significant performance loss. The antenna has a layered structure that allows the lowfrequency antenna array to have both a sufficient impedance bandwidth and realized gain. The antenna has a shared aperture since the highfrequency reflectarray has unit elements within the area of the lowfrequency patch antenna array. This allows the antenna to achieve a good realized gain in the high-frequency band. The proposed antenna is fabricated and measured. The prototype is designed for S-and Kaband resulting in a frequency-ratio of 7.37. The shared aperture size is 156 mm × 156 mm × 4.624 mm (1.82λ × 1.82λ × 0.05λ at S-band and 13.4λ × 13.4λ × 0.40λ at Ka-band). Measurements show the impedance bandwidth to be 200 MHz (6%) and 5.1 GHz (20%) and the peak realized gain to be 13.70 dBi and 27.65 dBi at 3.5 GHz and 25.8 GHz, respectively A very good agreement between the simulated and measured results is observed.

A beam-steerable 2-bit reflectarray antenna with an electromagnetic control mechanism is presented in this communication. The phase reflection of the proposed 2-bit reflectarray unit elements is altered by moving two pins between a patch and the ground plane. In the suggested concept, the pins are moved with electromagnetism. To prove the concept, a prototype with manually turned screws is evaluated through measurements to verify the reflectarray performance. The prototype antenna is measured to have an impedance bandwidth of more than 5 GHz. The boresight realized gain is measured to be 20 dBi at 25 GHz and a gain bandwidth is more than 2 GHz. Measurements show that the prototype antenna is able to beam-steer in a 120-degree range with a gain drop of less than 3 dB.

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